FieldsIO implementation for 0D to 2D cartesian grid fields, with MPI (#512)

* TL: added fieldsIO implementation to helpers

* TL: fixed the fieldsIO when mpi4py not available

* TL: SO IMPORTANT CHANGE THANKS BLACK !!!

* TL: cleaning and docstrings

* TL: added a small comment

* TL: tentative to solve static typing issue with no mpi4py

* TL: forgot black, ofc

* TL: introducing modern python tactics in ci 

* TL: attempt to solve the fenics tests

* TL: pip is a little trickster 

* TL: satisfying thomas's requests

* TL: seems like ruff is my new best friend

* TL: renaming grid[...] to coord[...]

* TL: last fixes